CVE-2024-35971 Affecting kernel-azure package, versions <6.4.0-150600.8.5.4
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-SLES156-KERNELAZURE-7347513
- published22 Jun 2024
- disclosed21 Jun 2024
Introduced: 21 Jun 2024
CVE-2024-35971 (opens in a new tab)How to fix?
Upgrade SLES:15.6 kernel-azure to version 6.4.0-150600.8.5.4 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-azure package and not the kernel-azure package as distributed by SLES.
See How to fix? for SLES:15.6 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
net: ks8851: Handle softirqs at the end of IRQ thread to fix hang
The ks8851_irq() thread may call ks8851_rx_pkts() in case there are any packets in the MAC FIFO, which calls netif_rx(). This netif_rx() implementation is guarded by local_bh_disable() and local_bh_enable(). The local_bh_enable() may call do_softirq() to run softirqs in case any are pending. One of the softirqs is net_rx_action, which ultimately reaches the driver .start_xmit callback. If that happens, the system hangs. The entire call chain is below:
ks8851_start_xmit_par from netdev_start_xmit netdev_start_xmit from dev_hard_start_xmit dev_hard_start_xmit from sch_direct_xmit sch_direct_xmit from __dev_queue_xmit __dev_queue_xmit from __neigh_update __neigh_update from neigh_update neigh_update from arp_process.constprop.0 arp_process.constprop.0 from __netif_receive_skb_one_core __netif_receive_skb_one_core from process_backlog process_backlog from __napi_poll.constprop.0 __napi_poll.constprop.0 from net_rx_action net_rx_action from __do_softirq __do_softirq from call_with_stack call_with_stack from do_softirq do_softirq from __local_bh_enable_ip __local_bh_enable_ip from netif_rx netif_rx from ks8851_irq ks8851_irq from irq_thread_fn irq_thread_fn from irq_thread irq_thread from kthread kthread from ret_from_fork
The hang happens because ks8851_irq() first locks a spinlock in ks8851_par.c ks8851_lock_par() spin_lock_irqsave(&ksp->lock, ...) and with that spinlock locked, calls netif_rx(). Once the execution reaches ks8851_start_xmit_par(), it calls ks8851_lock_par() again which attempts to claim the already locked spinlock again, and the hang happens.
Move the do_softirq() call outside of the spinlock protected section of ks8851_irq() by disabling BHs around the entire spinlock protected section of ks8851_irq() handler. Place local_bh_enable() outside of the spinlock protected section, so that it can trigger do_softirq() without the ks8851_par.c ks8851_lock_par() spinlock being held, and safely call ks8851_start_xmit_par() without attempting to lock the already locked spinlock.
Since ks8851_irq() is protected by local_bh_disable()/local_bh_enable() now, replace netif_rx() with __netif_rx() which is not duplicating the local_bh_disable()/local_bh_enable() calls.
References
- https://www.suse.com/security/cve/CVE-2024-35971.html
- https://bugzilla.suse.com/1224578
- http://www.openwall.com/lists/oss-security/2024/05/30/1
- http://www.openwall.com/lists/oss-security/2024/05/30/2
- https://git.kernel.org/stable/c/492337a4fbd1421b42df684ee9b34be2a2722540
- https://git.kernel.org/stable/c/49d5d70538b6b8f2a3f8f1ac30c1f921d4a0929b
- https://git.kernel.org/stable/c/be0384bf599cf1eb8d337517feeb732d71f75a6f
- https://git.kernel.org/stable/c/cba376eb036c2c20077b41d47b317d8218fe754f